The present invention relates to a magnetic tape recording and reproducing apparatus having a rotary head cylinder, and more particularly, to a magnetic tape recording and reproducing apparatus which can prevent vibration caused by rotation of a rotary drum constituting a rotary head cylinder.
A general magnetic tape recording and reproducing apparatus having a rotary head cylinder records a signal on a magnetic tape or reproduces the signal therefrom. Such a magnetic tape recording and reproducing apparatus uses a rotary head cylinder on which at least one head is installed in order to read recorded data from a magnetic tape or records data thereon. A case where such a rotary head cylinder is used in an apparatus requiring a high speed rotation and a high density recording such as a digital video cassette recorder (VCR) will be described with reference to FIG. 1.
FIG. 1 is a sectional view showing a rotary head cylinder for use in a conventional magnetic tape recording and reproducing apparatus. The rotary head cylinder shown in FIG. 1 includes a cylindrical rotary drum 10 which rotates at high speed, a cylindrical static drum 20 which is located in the lower side of the rotary drum 10, and a shaft 18 which penetrates the central axis of the rotary drum 10 and the static drum 20 and is inserted into a through-hole 32 provided in the static drum 20.
The rotary drum 10 is connected with the shaft 18 via a bearing 16, and includes a motor unit 12 for rotation of the rotary drum 10 therein. The rotary drum 10 has the same diameter as the upper portion of the static drum 20. A head 14 for recording data on a magnetic tape or reproducing data therefrom is installed on the edges in the lower surface of the rotary drum 10. The head 14 is disposed so that it is embedded by a minute distance from the circumferential surface of the rotary drum 10 toward the shaft 18. A tape lead 22 for guiding the magnetic tape is formed on the outer circumferential surface of the static drum 20. The tape lead 22 guides the magnetic tape via contact to the magnetic tape so that the head 14 can facilitate a recording and reproduction operation with respect to the magnetic tape.
Fixed protrusions 26 formed on the upper surface of a drum base 24 are inserted into insertion holes 28 formed on the lower edges of the static drum 20. Screw grooves 34 for fixing the static drum 20 to the drum base 24 are formed between the insertion holes 28. A number of the screw grooves 34 are installed in the lower surface of the static drum 20 in the form of surrounding the shaft 18, and are individually connected with fixed screws 30. The static drum 20 is fixed to the drum base 24 by such a screw coupling.
The rotary head cylinder having the above-described structure does not have a complete symmetrical structure by weight around a rotational axis. As a rotary head cylinder becomes compact, a static drum is fabricated to become thinner and thinner as well. Therefore, when such a rotary head cylinder rotates at high speed, an axial vibration occurs. The axial vibration deforms the thin static drum 20 in thickness even though a small amount of load is applied to the rotary head cylinder. That is, the vibration shock caused by the rotary drum 10 is transferred to the static drum 20 via the shaft 18, to thereby deform the shape of the thin static drum 20. Such a deform of the static drum causes the tape lead 22 not to guide a magnetic tape well. As a result, the head installed on the rotary drum 10 does not trace accurately with respect to the magnetic tape.
Also, in the case of a camcorder, noise generated by the rotary head cylinder may be recorded on a mantic tape together with a recording signal.